In recent years, semiconductor integrated circuit elements (semiconductor chips) used as a microprocessor of a computer, etc. have developed a lot in speed and in their functions, and in accompany with this, the number of its terminals increases and there is a tendency that pitches between the terminals also become narrower. Generally, on a bottom of the semiconductor chip, a large number of connection terminals are arranged, and respective connection terminals of the semiconductor chip are connected to the multiple connection terminal portions, which are formed on a wiring board, for mounting the semiconductor in flip chip form.
For example, a wiring board for flip-chip connecting has been proposed for a peripheral type semiconductor chip such that a large number of connection terminals are arranged along an outer circumference of the chip bottom (for example, refer to PTL 1). In this wiring board, a chip mounting area in a rectangular shape corresponding to an outer shape of the semiconductor chip is set up on a substrate principal surface, and the multiple connection terminal portions are disposed in a way such as to be along an outer circumference of the chip mounting area. The multiple connection terminal portions are provided in a part of belt-like wiring conductors. The wiring conductor itself is covered by a solder-resist layer provided on the substrate principal surface as a resin insulating layer of the outermost layer, and almost whole of the wiring conductor is put in an unexposed state. On the other hand, the surface of each connection terminal portion is exposed to the outside through an opening provided in the solder-resist layer. Then, each exposed connection terminal portion and the connection terminal on the semiconductor chip side are arranged facing each other, and they are configured to be electrically connected with each other through a solder bump etc.
Further, in a wiring board 101 of this kind, as a part of increasing the number of terminals and narrowing a pitch therebetween, for example, in an opening 103 of a solder-resist layer 102, it is being tried that different wiring conductors are arranged at predetermined positions so as to pass through between multiple wiring conductors 105 having connection terminal portions 104 (refer to FIG. 15). However, in the case where wiring conductors 106 are arranged at predetermine positions between the wiring conductors 105 having the connection terminal portions 104, the connection terminal portions 104 and the wiring conductors 106 become too close in distance and mutual insulation distances are no longer secured. For this reason, there is a possibility that a short defect may occur at the time of solder connection. As its measure, it is necessary to achieve isolation of the wiring conductors 106 located in the opening 103 from adjacent connection terminal portions 104 by covering them with a part of the solder-resist layer 102 (being called a “dam portion 107” for convenience).
Here, a procedure of manufacturing the wiring board 101 shown in FIG. 15 will be explained. First, the wiring conductors 105, 106 are formed by forming a copper plating layer on a resin insulating layer 108 and etching this. Next, a photosensitive resin insulating material that becomes the solder-resist layer 102 later is applied on the resin insulating layer 108 to form a resin insulating material layer 109 that covers the wiring conductors 105, 106 (refer to FIG. 16). Next, on the resin insulating material layer 109, a photomask 110 is placed and ultraviolet rays 112 are irradiated thereon through the photomask 110 in this state. Then, the ultraviolet rays 112 contact the area that becomes directly under a light passage portion 111 of the photomask 110 fundamentally, and the area in the resin insulating material layer 109 is exposed selectively. In FIG. 16, a dashed line shows an exposure portion 113. After this, the exposed resin insulating material layer 109 is developed (refer to FIG. 17) and is also cured by heat or ultraviolet rays, and an outermost surface treatment, such as plating, is performed on the wiring conductors 105 exposed to the surface. As a result, the wiring board 101 having the precise dam portion 107 is completed (refer to FIG. 18).